Is hemophilia genetic?

i think that about sums it up.

Yes, it is. It is a sex-linked disease. The disease is carried on an X chromosome, and generally occurs in males. That sounds contradictory, so I'll try to explain.

A male has one X and one Y chromosome. You might think of the "Y" as being an "X" with one leg missing, however. The missing leg corresponds to the "leg" on the X chromosome where the gene for the clotting factor resides. In a woman who is a carrier, she has two X chromosomes, as all women do. On on "leg" of one of those X chromosomes is the defective gene. However, since the woman has two X chromosomes, the good chromosome on the OTHER X that she has takes care of the problem by producing the clotting factor that she needs when she's injured.

If, however, a boy inherits the defective gene on an X chromosome from his mother (he has a 50-50 chance if she is a carrier, as all she has to give are X chromosomes), then because his father's Y chromosome is missing that "leg", there's no working copy of the chromosome to produce the clotting factor, and so he is a hemophiliac. He can't get the healthy X chromosome from his father, because the genetic contribution of a father to a son is always a Y (otherwise, he'd be female).

Theoretically, a woman could be a hemophiliac if her mother were a carrier, AND her father were himself a hemophiliac. In that case, if she got her mother's defective X AND the defective X that caused her father's hemophilia (because he only has one), then she would have two "bad" X chromosomes, and she would be a hemophiliac because neither of her X chromosomes would have a working gene to make the clotting factor. Such a woman would probably not live past puberty, however, as she would almost certainly hemorrhage severely when she started having menstrual periods.